1. Field of the Invention
The invention in the field of pharmaceutical science and biomedicine relates to novel formulations of fenretinide (N-4-hydroxyphenylretinamide) in the form of lipid nanoparticles, solid dispersions and emulsions that avoid undesirable components that cause hypersensitivity reactions.
2. Description of the Background Art
Fenretinide (4-hydroxyphenyl-retinamide, abbreviated as HPR or 4-HPR, each of which is used interchangeably herein)) is a synthetic Vitamin A analog of Formula 1, below.
HPR was initially developed as a less toxic, better-tolerated amide analog of retinoic acids for chemoprevention of cancer. Trials of HPR as a chemopreventive agent for breast cancer have been disappointing, although it was active in actinic keratosis (Moglia, D et al., 1996, Cancer Lett 110:87-91) a precursor condition to squamous cell carcinoma of the skin.
More recent studies showed that micromolar concentrations of HPR, acting independently of retinoid receptors RAR or RXR, induced apoptosis in human tumor cell lines. HPR had a favorable safety profile after parenteral administration. A dose finding study in animals evaluated 100 to 1800 mg HPR/kg/day administered IP for 21 days; the agent was in a suspension in Cremophor®-polyethylene glycol-water (8:10:82) and identified a mouse LD10 (lethal dose in 10% of the animals) of 217 mg/kg (651 mg/m2) (Sani, B P et al., 1983, Toxicol Appl Pharmacol 70:228-235). A subsequent toxicity study of this dosage form and regimen in Swiss mice and Sprague-Dawley rats revealed lethality and liver and bone marrow toxicity at the LD50 but not at the ½LD10 or LD10. Thus, daily doses as high as ˜600 mg/m2 for 21 days were well tolerated in rodents. Clinical trials of chronic, low dose oral HPR in high-risk breast cancer patients confirmed that it was well tolerated and without cumulative dose toxicity.
The National Cancer Institute (NCI), interested in exploring higher doses of HPR as a cytotoxic agent for chemotherapy of advanced solid tumors, acquired the rights to this compound for cancer chemotherapy indications as well as the entire supply of clinical grade HPR.
Since the mid-1970s, oral HPR has been studied in animal models of cancer chemoprevention (Moon, R C et al. (1979) Cancer Res 39:1339-46; Moon, R C et al. (1982) Carcinogenesis 3:1469-72; Pollard, M et al., (1991) Cancer Lett 59:159-63; Welsch, C W et al., (1983) Carcinogenesis 4:1185-87; Chan, L et al., (1997) Leuk Lymphoma 25:271-80) and in human tumor xenograft models of therapy (Dowlatshahi, K et al., (1989) Canc Lett 47:187-92; Pienta, K J et al. (1993) Cancer Res 53:224-6). HPR was administered in the food or by gavage in a corn oil-ethanol suspension at daily doses from 300-1200 mg/kg/day (0.7-3 mmol/kg) though these studies did not evaluate pharmacokinetics. In separate pharmacokinetic studies, oral doses of 25 and 125 mg/kg/day for 10 days achieved plasma levels of 80 and 260 ng/mL measured 3 hrs after the last dose (Kenel, M F et al., (1988) Teratog Carcinog Mutagen 8:1-11). There was a similar increase in the level of the primary metabolite “MPR,” the 4-hydroxymethyl derivative of HPR.
An important and perhaps overlooked finding in this study was that an additional 6.5-fold increase in daily dose (from 125 to 800 mg/kg/day) failed to achieve additional increases in plasma HPR (260 and 315 ng/mL) or in the MPR metabolite (60 and 60 ng/mL), suggesting an upper limit on achievable systemic levels using the corn oil-based oral formulation. Such an upper limit severely limits the usefulness of HPR as a chemotherapeutic because plasma concentrations cannot reach cytotoxic levels even if the dose is escalated well-above chemoprevention levels. Thus, one objective of the present inventors was to develop formulations and dose regimens s that would overcome these limitations.
Retinoic acids are soluble in aqueous solvents and can be entrapped inside lipid vesicles. In contrast, HPR and other neutral retinoids exhibit very low water solubility and high octanol:water partition coefficients. Based on these properties, earlier studies by some of the present inventors explored two formulation strategies (i) a protective polymer interface that gradually released HPR as it hydrolyzes, and (ii) solubilizing HPR in water soluble (amphipathic) lipid vesicles or emulsions to take advantage of its natural affinity for lipid membranes.
Protective polymer interfaces used block co-polymers and solid dispersion technology. In the latter, drug solubility is increased by disrupting the crystal structure of the drug by solid-state dispersion into hydrophilic carrier molecules, which replace the drug molecule in the crystal lattice. A key discovery for reducing particle size and increasing dissolution rate involved eutectic mixtures of poorly soluble drugs with physiologically inert carriers such as urea to avoid aggregation and agglomeration in the powder state. This approach evolved into the use of a solid solution in which a drug is molecularly dispersed in a soluble carrier (Chiou, W L et al. (1971) J Pharm Sci 60:1569-71; Chiou, W L (1977) J Pharm Sci 66:989-91).
The highly investigational nature of newer formulation technologies such as block co-polymer and solid dispersion is a drawback due to (i) the slowing of the time-to clinic as compared to liposomal formulations and (ii) the risk of unanticipated safety problems of excipients.
The minimum HPR exposure level required to inhibit human tumor cell lines in vitro by at least 50-90% is 10 μM for 72 hours as discovered in the following model systems: clonogenic assays of fresh biopsy specimens (Meyskens, F L et al. (1983) Int J Canc 32:295-99); neuroblastoma cell lines (Mariotti, A et al., (1994) J Natl Canc Inst 86:1245-47); small cell lung carcinoma (SCLC) (Kalemkerian, G P et al., (1995) J Natl Cance Inst 87:1674-80); prostate carcinoma (Pienta, K et al., supra; Hsieh, T C et al., (1995) Biochem Mol Biol Int 37:499-506); breast carcinoma (Marth, C et al., (1985) J Natl Cancer Inst 75:871-875); and cervical cancer (Oridate, N. et al., (1995) J Cell Biochem Suppl 23:80-86).
One goal of the present inventors was the discovery of improved compositions and methods for treating pancreatic cancer. Despite its relatively lower incidence, pancreatic cancer has become the fourth leading cause of cancer related deaths (preceded by lung, breast/prostate and colorectal cancer) among both male and female adults in the United States with an estimated 28,200 deaths in 2000 (Greenlee, R T et al., (2000) CA Cancer J Clin 50:7-33). No effective method of early diagnosis of this disease is presently available, so pancreatic cancer is commonly diagnosed late in its natural history. It is highly resistant to conventional therapies such as surgical resection or chemotherapy with the nucleoside analog gemcitabine (Gemzar®). Survival is usually 5-9 months. Mortality rates essentially equal disease incidence. Gemcitabine is currently the first-line treatment for patients with locally advanced (nonresectable Stage II or Stage Ill) or metastatic (Stage IV) adenocarcinoma of the pancreas. Several drugs (Irinotecan, oxaliplatin, docetaxel, etc.) are being studied in combination with gemcitabine. F. Patterson et al., 2001, Pancreas. 23:273-9) reported that retinoic acid enhanced the cytotoxic effects of gemcitabine and cisplatin in pancreatic adenocarcinoma cells.
The present inventors' results on xenografts of Bx-PC3 pancreatic tumors revealed activity of HPR, administered intravenously (IV) in a preclinical model. Although oral HPR is in Phase II clinical trials, this dosage form failed to achieve target plasma levels in a Phase I trial, motivating the present inventors to develop new IV formulations. In studies conducted by some of the present inventors and colleagues (Vaishampayan, U et al., 2005, Invest. New Drugs 23:179-85), HPR levels in renal cell carcinoma (RCC) biopsies from three patients treated with oral HPR were measured and found to be below those required to induce human tumor cell apoptosis in vitro, which was consistent with the minimal or negative clinical efficacy in this trial (several patients with stable disease but no remissions). Kalemkerian et al. reported moderate effectiveness of HPR in treatment of SCLC patients noted as stable disease in 30% of advanced patients, despite suboptimal plasma concentrations. The foregoing studies point to the significant medical and commercial need for an effective IV dosage form of HPR and methods using this formulation for treatment of pancreatic cancer, RCC and other forms of cancer that overcomes the problem arising from limited blood levels due to poor and limited absorption of orally administered HPR.
Lipid-Based and Polymer-Based Formulations
Parenteral emulsions are finding increasing use as carriers for drugs because of their ability to incorporate drugs into their innermost phase, thus minimizing or bypassing solubility and stability constraints (Andreu, A et al., (1992) Ann Pharmacother 26:127-8; Singh, M et al., (1986) J Parenter Sci Technol 40:34-41; Lundberg, B. (1994) J Pharm Sci 83:72-5; Prankerd, R J et al., (1988) J Parenter Sci Technol 42:76-81; Benita, S et al., (1993) J Pharm Sci 82:1069-79). Examples of emulsion formulations include the drugs penclomedine, a practically insoluble antitumor agent (Prankerd et al., supra), taxol (Tarr, B D et al., (1987) Pharm Res 4:162-65), diazepam (Levy, M Y et al. (1989) Pharm Res 6:510-516; Levy, M Y et al., (1991) J Parenter Sci Technol 45:101-7), and propofol (Han, J et al., (2001) Int J Pharm 215:207-20).
Liposomes can be customized to modify drug release and (a) target drugs to the reticulo-endothelial system (RES), (b) avoid drug uptake by the RES, and (c) target tumors or other specific tissue sites. Apart from solving the solubility problem, liposomal preparations may achieve target specific drug delivery, prolong the duration of action, reduce the toxicity and thus improve the therapeutic index. For example, doxorubicin in liposomes was found to be 100-times more effective than free drug against liver metastasis of the M5076 tumor (Mayhew, E et at. (1983) Cancer Drug Deliv 1:43-58; Mayhew, E et al. (1985) Prog Clin Biol Res 172B:301-10). Liposomal encapsulation of amphotericin B, a potent, but extremely toxic, antifungal drug, resulted in an effective product with reduced toxicity. The potential of liposomes and related systems for drug delivery has been realized in several FDA approved intravenous liposomal and lipid-complexed products: Amphotericin B (ABELCET®, Amphotec®, and AmBiosome®), Doxorubicin (Doxil®, Caelyx®), and Daunorubicin (Daunoxome®). For a disease that involve the RES (e.g., leishmaniasis, or a case in which a liposomal system needs to be made tumoricidal by attaching tumor-specific antibodies, a conventional liposome that is “visible” to fixed tissue macrophages is preferable. In contrast, in another context—artificial blood using hemosomes—lipid vesicles must be “invisible” and avoid RES recognition.
One of the present inventors, R. R. Boinpally, and his colleagues identified several variables in preparation of lipid vesicles that enhance delivery to tissues outside the RES (Gopi N et al., 2002, J Colloid Interface Sci. 251:360-65; Gopinath, D et al., 2001, Arzneimittelforschung 51:924-30; Gopinath, D et al., 2002, Int J Pharm 246:187-97; Boinpally R et al., 2001, J Contr Rel Ann Symp Suppt; Boinpally R, et al., 2001, AAPS Pharm Sci Ann Mtg Suppl 3(3).
Although more soluble retinoic acid drugs like Tretinoin and Iso-tretinoin are available as parenteral dosage forms, and even as encapsulated lipid products (as well as creams and gels), parenteral dosage forms for poorly soluble, neutral retinoid compounds like HPR have never been approved by the FDA, despite a large number of available analogs and numerous reports about their promising anti-cancer potential (Douer D et al., (2000) in ASCO Abstr 538; Douer, D et al., 2001, Blood 97:73-80).
Studies by the present inventors' laboratories showed that the natural solubility of HPR in aqueous buffer like phosphate buffered saline at pH 7.4 is <1 μg/ml. Although the compound is readily soluble in ethanol, this solvent solubility was not maintained when an ethanol solution of HPR was mixed into aqueous buffered systems, like physiological solutions, and in fact, even when the ethanol content of an aqueous solution of HPR was as high as 20%, the HPR solubility only reached approximately 1-2 μg/ml. Inclusion physiological proteins found in human blood plasma like high density lipoprotein, retinol binding protein, albumin, and al-acid-glycoprotein did not increase HPR solubility to therapeutic levels either, as shown in Table 1, below.
TABLE 1Maximum Solubility of HPR in Physiological ConditionsMaximum HPRAqueous SystemAdditiveSolubilityPhosphateNoneLess than 1μg/mlbuffered saline,Ethanol to 20% of volume1-2μg/ml(PBS), pH 7.4High density lipoprotein, 0.2 g/L1.5-3μg/mlRetinol binding protein, 0.05 g/L<1μg/mlAlbumin, 50 g/L7-8μg/mlα1-acid-glycoprotein, 1 g/L1-2μg/ml
Related subject matter is described in the following U.S. patents and patent publications of B. J. Maurer and colleagues: U.S. Pat. Nos. 6,352,844 and 6,368,831; U.S. Patent publications, 2005/010167, 2005/0106216, 2005/0187186, 2005/0271707, and 2006/0008508. U.S. Pub. 2002/0183394 and U.S. Pat. No. 7,169,819 (Gupta et al.) disclose of methods of preparing liposomal compositions of HPR and/or other retinoids, liposomal HPR compositions prepared by such methods, and use of such compositions in the treatment of diseases, such as breast cancer. The compositions and methods are distinct from those of the present invention. U.S. Pat publication 2002/0143062 of Lopez-Berestain et al. discloses a pharmaceutical composition for parenteral delivery, that comprises a retinide such as HPR in combination with a solvent capable of dispersing or solubilizing the retinide. The solvent comprises an alcohol, such as ethanol, in combination with an alkoxylated castor oil, such as Cremophor®-EL, or in an emulsion composed of HPR and a lipoid dispersed in an aqueous phase, a stabilizing amount of a non-ionic surfactant, optionally a solvent, and optionally an isotonic agent. In addition, a method of use in the treatment of hyperproliferative disorders, such as cancers is described. These compositions and formulations are distinct from the those of the present invention.
To summarize, the clinical potential of HPR as a chemotherapeutic agent has never been realized because existing pharmaceutical technology is limited to oral HPR formulations that cannot achieve therapeutic plasma concentrations. There is thus a need in the art for IV or other parenteral dosage forms of HPR that circumvent these problems and achieve plasma levels adequate to effect cancer cell apoptosis and other clinically desirable effects.
The present formulations, particularly those for intravenous administration of neutral retinoids such as HPR represents the clinical introduction of an appropriate dosage form that can achieve low micromolar concentrations for a “first-in-class retinoid” that induces apoptosis (via pathways independent of RAR/RXR) and has demonstrated efficacy in human tumor models. The present formulations thus have substantial market advantages over those of the prior art and offer clinicians well-tolerated products for treatment of various diseases, including pancreatic cancer and other solid tumors.